I have fired some small pistols that I considered to be very accurate, but I guess the most accurate of the smaller pistols would be the HK P7M8. Shooting carefully from a rest at 25 yds., my P7M8 has shot groups as small as with the SIG P210s. The P210s, obviously larger, with black sights,etc, produce small groups, for me,more routinely than any of the other pistol I can recall shooting. It is harder to accomplish with the HK, just due to it's smaller size and white highlighted "combat" style sights, but the intrinsic accuracy is sure there IMHO.....ymmv
BTW, My honorable mention for small accurate pistols would have to go to the little S&W models 3913 and 3914 single stack 9MMs. Really surprising for a super reliable little production CCW type 9MM...